Osteosarcoma / Ewing Sarcoma¶
Definition¶
Osteosarcoma and Ewing sarcoma are primary malignant bone tumors that rarely affect the spine but are important diagnostic considerations, particularly in young patients. Both are aggressive tumors with different histological origins and imaging features.
Osteosarcoma of the Spine¶
Epidemiology¶
Spinal osteosarcoma is rare, accounting for 3–5% of all osteosarcomas. It typically affects patients in their 30s–40s (older than appendicular osteosarcoma) and is associated with prior radiation therapy (secondary osteosarcoma) and Paget disease.
Imaging¶
CT: - Destructive mass centered on the vertebral body, often extending into posterior elements - Osteoid matrix — Amorphous, cloud-like calcification/ossification within the mass (the hallmark of osteosarcoma) - Cortical destruction with periosteal reaction - Large soft tissue component
MRI: - Low to intermediate T1, heterogeneous T2 signal - Areas of low T2 signal correspond to osteoid matrix - Epidural extension with cord compression is common - Avid enhancement
Ewing Sarcoma of the Spine¶
Epidemiology¶
Ewing sarcoma is the second most common primary bone malignancy in children and young adults. Spinal involvement accounts for approximately 8% of all Ewing sarcomas, most commonly in the sacrum. Peak age is 10–20 years.
Imaging¶
CT: - Permeative lytic bone destruction (aggressive pattern) - Large associated soft tissue mass, often much larger than the bony component - Periosteal reaction (lamellated or "onion-skin" pattern) - No matrix mineralization (unlike osteosarcoma)
MRI: - Low T1, intermediate-to-high T2 signal - Homogeneous enhancement - Large soft tissue component that often extends through the neural foramina - Marrow edema and cord compression may be present
Clinical Pearl
In the spine, the key imaging distinction between osteosarcoma and Ewing sarcoma is matrix mineralization. Osteosarcoma produces osteoid matrix (amorphous cloud-like calcification on CT), while Ewing sarcoma does not. Ewing sarcoma typically produces a larger soft tissue mass relative to the degree of bony destruction. Both are aggressive, destructive lesions in young patients.
Key Points¶
- Spinal osteosarcoma is rare, often secondary to radiation or Paget disease, and produces osteoid matrix
- Ewing sarcoma is most common in the sacrum in patients aged 10–20
- Ewing sarcoma produces a large soft tissue mass without matrix mineralization
- Both are aggressive, destructive tumors requiring biopsy for definitive diagnosis
- MRI evaluates epidural extension and cord compression; CT characterizes matrix and cortical destruction
References¶
- Ilaslan H, Sundaram M, Unni KK, Shives TC. Primary vertebral osteosarcoma: imaging findings. Radiology. 2004;230(3):697-702.
- Ilaslan H, Sundaram M, Unni KK, Dekutoski MB. Primary Ewing's sarcoma of the vertebral column. Skeletal Radiol. 2004;33(9):506-513.
- Katonis P, Datsis G, Karantanas A, et al. Spinal osteosarcoma. Clin Med Insights Oncol. 2013;7:199-208.
- Green R, Saifuddin A, Cannon S. Pictorial review: imaging of primary osteosarcoma of the spine. Clin Radiol. 1996;51(5):325-329.
- Gaillard F, et al. Osteosarcoma. Radiopaedia.org. Available from: https://radiopaedia.org/articles/osteosarcoma
- Gaillard F, et al. Ewing sarcoma. Radiopaedia.org. Available from: https://radiopaedia.org/articles/ewing-sarcoma